Method of contact transfer of developed electrostatic images

ABSTRACT

Our invention contemplates a novel method of contact transfer of developed electrostatic images and means for carrying out our process. In our method, a photoconductive surface is exposed to a pattern of light and shade as done in known electrophotographic processes. Our toner, however, is not a dry powder nor do we employ a known liquid developer. Instead we use a liquid developer which carries a toner which is tacky. This tackiness, however, is a transient one. After the latent electrostatic image is developed by our tacky toner, that is one that has adhesive properties, the developed image with the toner in tacky state is contacted with sheet material such as paper. The developed tacky toner image has greater affinity for the paper than it does for the photoconductive surface. After the image is transferred to the sheet material the toner quickly loses its tackiness and dries to a hard scuff-resistant surface. Our invention also contemplates a developer liquid which contains a toner which is non-sticky when first deposited then becomes sticky or tacky so that it can be transferred while tacky and loses its tackiness and remains firmly bonded to the surface to which it is transferred. The developing liquid comprises a low-boiling organic liquid which has low solvent power for a sol comprising a high molecular-weight polymer and a finely divided pigment or toner material adapted to be attracted by the charges on the photoconductive surface. The organosol contains modifiers and plasticizers adapted to give the developer liquid the desired characteristics.

United States Patent [1 1 Smithet al.

[ METHOD OF CONTACT TRANSFER OF DEVELOPED ELECTROSTATIC IMAGES [75]Inventors: Ian Edward Smith, Lockleys; Peter John I-Iastwell, ElizabethGrove; Marinus Cornelus Vermeulen, Valley View, all of Australia [73]Assignee: Savin Business Machines Corporation, Valhalla, NY.

[22] Filed: June 21, 1971 [21] Appl. No.: 155,108

[52] US. Cl. 96/l.4, 96/1 LY, 96/1.8, 96/1.5, 117/6, 117/37 LE, 96/83,252/621, 355/10, 118/637 [51] Int. Cl G03g 13/14 [58] Field of Search96/1 LY, 1.4, 1.8, 83;

117/37 LE, 6; 252/621 LR I [56] References Cited UNITED STATES PATENTS3,025,160 9/1962 Bunge et al 96/l.8 3,080,250 3/1963 Claus 117/37 LE3,244,633 4/1966 Yellin et al. 117/37 LE 3,275,436 9/1966 Mayer 96/1.43,301,698 1/1967 Fauser et al. 96/1 LY 3,391,015 7/1968 Fauser......117/37 LE 3,446,616 5/1969 Clark 96/1.5 3,464,820 9/1969 Michaelchik96/I.8 3,507,794 4/1970 Fauser et al. 117/37 LE 3,535,244 10/1970 Zabiak117/37 LE 3,592,642 7/1971 Kanpp 96/l.4 3,716,360 2/1973 Fukushima etal. 96/1 LY X FOREIGN PATENTS OR APPLICATIONS 2,008,251 1/1970 France96/1.4 1,913,173 6/1970 Germany 96/l.4

[ Oct. 1, 1974 Primary ExaminerRoland E. Martin, Jr.

Attorney, Agent, or Firm-Shenier & OConnor [5 7] ABSTRACT Our inventioncontemplates a novel method of contact transfer of developedelectrostatic images and means for carrying out our process. In ourmethod, a photoconductive surface is exposed to a pattern of light andshade as done in known electrophotographic processes. Our toner,however, is not a dry powder nor do we employ a known liquid developer.Instead we use a liquid developer which carries a toner which is tacky.This tackiness, however, is a transient one. After the latentelectrostatic image is developed by our tacky toner, that is one thathas adhesive properties, the developed image with the toner in tackystate is contacted with sheet material such as paper. The developedtacky toner image. has greater affinity for the paper than it does forthe photoconductive surface. After the image is transferred to the sheetmaterial the toner quickly loses its tackiness and dries to a hardscuff-resistant surface.

Our invention also contemplates a developer liquid which contains atoner which is non-sticky when first deposited then becomes sticky ortacky so that it can be transferred while tacky and loses its tackinessand remains firmly bonded to the surface to which it is transferred. Thedeveloping liquid comprises a low-boiling organic liquid which has lowsolvent power for a sol comprising a high molecular-weight polymer and afinely divided pigment or toner material adapted to be attracted by thecharges on the photoconductive surface. The organosol contains modifiersand plasticizers adapted to give the developer liquid the desiredcharacteristics.

7 Claims, 6 Drawing Figures PATENTEDUBT 11974 sum 1 or s INVENTORSSmI-fh [0/7 Edumra Mari/705 Came/05 Vermeu/efl PATENIEDUBT 1 m4 SHEET t0F 5 5 mhdm w. TMHWM N N f R m V a V55 4 T N 05 T 1 HMS 4 d w+ rflr WZ3J 5 Mg me PM 5 METHOD OF CONTACT TRANSFER OF DEVELOPED ELECTROSTATICIMAGES BACKGROUND OF THE INVENTION Electrostatic reproduction processesare well known to the art. In the well-known Xerox system aphotoconductive surface carried by a drum is electrostatically chargedby a corona discharge device. The photoconductive surface which may beof selenium or the like is an insulator in the dark and a conductor inthe light. The image to be reproduced is focused on the photoconductivesurface. When the light strikes the photoconductive surface the chargeleaks away in the illuminated areas leaving the dark areas to form theimage. The latent image in the form of electrostatic charges on he nhqteqnquqtive. urfessis-thszmdexelenelm a;

toner. This toner must be in the form of a dry powder. The dry tonerparticles are then transferred by an electrostatic charge to sheetmaterial such as ordinary paper and are usually formed fromthermosplastic resins. The toner particles are then fixed by heat on theordinary paper and the image appears in its final form. The necessity ofusing heat to fix the toner particles prevents high-speed operation ofthe Xerox system. Furthermore, the dry toners are slightly abrasive andsooner or later they scratch and mar the selenium surface of the drumwhich is the heart of the Xerox machine. The dry toner also causesmechanical problems since the toner particles become air-borne andpermeate the bearings of the machine. This requires frequent cleaning,which is an onerous task. The dry toners have inherent dielectrophoreticproperties which prevent their filling in large black areas. This iseasily observed by viewing any copy which has a large, black area madeon the Xerox machine.

In the Electrofax method, a sheet of paper is covered with aphotoconductor such as zinc oxide. The latent electrostatic image can bedeveloped either by a dry toner or by a liquid in which a toner issuspended. A liquid developer comprises finely divided pigment particleshaving an average size no larger than about 20 microns and probably muchsmaller to about an average size of about 5 microns, suspended in arelatively nonconductive light hydrocarbon such as benzene, zylene,hexane, naphtha, cyclohexane, or the like. The final image, of course,in the Electrofax process, appears on the photoconductor-coated surfaceand is not transferred to ordinary paper. It has been realized for sometime by those skilled in the art that it would be desirable to useliquid developers in a transfer process. No

one has found a way, however, to accomplish this conveniently. In US.Pat. No. 3,251,688 issued May 17, 1966, to Mihajlov, one attempt at theemployment of liquid developers in a transfer process is shown. Mihajlovapplies a film of liquid developer over the photoconductive surface. Hethen exposes the photoconductive surface and the developersimultaneously to a pattern of light and shadow. He then attempts totransfer the image to an ordinary paper. He has found, however, that thenon-image areas have background toner. He attempts to reduce this byapplying an electrical potential of the same polarity as that of thetoner to the roll which presses the paper against the film of developerand makes the roller of conductive rubber or the like.

In all of the processes of the prior art in which transfer of an imageis made from a photoconductor to ordinary paper, there is a loss ofdefinition according to the application of pressure which distorts thedeveloped image or through the difficulty of attaining effectivetransfer of development particles to a new location and the effectivefixing of the same. Difficulty is also experienced when the samephotoconductive surface is used repetitively, and images produced on itsuccessively are transferred to another medium. The problem is that thephotoconductive surface becomes soiled. This soiling is not very greatwhen dry toners are used but in a method such as that of Mihajlov, theliquid toner will adhere to some extent to the photoconductive surfaceand gradually become unuseable.

SUMMARY OF THE INVENTION One object of our invention is to provide anovel method of contact transfer of developed electrostatic images fromthe surface of a photoconductor to sheet material such as paper.

Another object of our invention is to provide a novel method of contacttransfer of electrostatic images developed by a liquid developer toordinary paper or the like.

Another object of our invention is to provide a novel method of contacttransfer of a liquid toner developed electrostatic image from thephotoconductive surface in an expedient and simple manner without theuse of an electrostatic field.

Still another object of our invention is to provide a method of contacttransfer of liquid toner developed electrostatic images whilemaintaining high resolution.

A further object of our invention is to provide a method of contacttransfer of a liquid toner developed electrostatic image from aphotoconductive surface to a copy sheet while maintaining thephotoconductive surface in a clean condition.

Another object of our invention is to provide a photoconductive surfacehaving less affinity for the developed electrostatic image than for thepaper to which it is to be transferred.

Another object of our invention is to provide an improved liquid toneror developer which can readily be applied to a latent electrostaticimage on a photoconductive surface from which it can readily betransferred to a second surface such as ordinary paper or the like.

A further object of our invention is to provide a novel liquid toner ordeveloper which is non-sticky when first deposited, becomes sticky ortacky after deposit so it can be transferred while tacky and loses itstackiness and remains firmly bonded to the surface to which it istransferred.

Another object of our invention is to provide a toner which can betransferred while tacky to a dry surface and then cured to provide ascuff-free and abrasionresistant final image.

Still another object of our invention is to provide a developer or tonerwhich when tacky will have greater affinity for paper than thephotoconductive surface on which the image was developed.

A further object of our invention is to provide a novel apparatus forcarrying out our novel method.

A further object of our invention is to provide a novel sheet materialhaving affinity for a tacky toner developed image.

Other and further objects of our invention will appear in the followingdescription.

In general, our invention contemplates the provision of aphotoconductive surface which may be carried by a drum or moving belt orthe like. The surface is adapted to be charged electrostatically by acorona discharge device which is well known in the art. The originalwhich is to be copied or reproduced is projected upon the chargedsurface. Where light strikes, the charge is conducted to ground throughthe photoconductor leaving a pattern of charges such as electronsfaithfully reproducing the image in a latent fashion. The latent imageis then developed with a liquid toner having transient adhesive or tackyproperties. The toner composition has low adhesion for the imageformingsurface and high-adhesion for the copy surface. The tacky or adhesiveproperties are transient and the final image exhibits high resolutionand is scufffree. While our invention contemplates the use of ordinarypaper, other appropriate sheet material such as thin sheets of plastic,aluminum foil or the like may be used if desired. The copy paper may becoated with a thin film of synthetic resin for which the toner particlessuspended in the developer liquid have affinity. This procedure willpermit a wider variety of developer liquids to be used. This eliminatesthe criticality or close limits of components in the confection of thedeveloper liquids.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings whichform part of the instant specification and which are to be read inconjunction therewith and in which like reference numerals are used toindicate like parts of the various views:

FIG. 1 is a diagrammatic sectional view of a photocopier adapted tocarry out the method of our invention and embodying one fonn of theapparatus of our invention.

FIG. 2,is a diagramatic view showing the driving train for thephotocopier shown in FIG. 1.

FIG; 3 is a circuit diagram showing the control circuit for thephotocopier shown in FIG. 1.

FIG. 4 is a diagramatic sectional view similar to that shown in FIG. 1showing another embodiment of apparatus involving our invention andcapable of carrying out the process of our invention.

FIG. 5 is a diagramatic view similar to that shown in FIG. 1 ofapparatus adapted to make a printing roller by the process of ourinvention.

FIG. 6 is a diagramatic view showing the printing roller made by theapparatus shown in FIG. 5 assembled in a machine for making Xerographicprints in rapid succession.

DESCRIPTION OF THE PREFERRED EMBODIMENT More particularly referring nowto the drawings, in FIG. 1 the photocopier indicated generally by thereference numeral 10 comprises a light-tight housing 12 in which weposition a rotary drum l4 bearing a photoconductive layer 16. Drum 14 ismade of conductive material and carries a photoconductive layer 16 wewill describe in greater detail hereinafter. Mounted on top of thehousing 12 is a carriage 18 adapted to reciprocate on suitable bearings20. The carriage 18 supports a transparent plate 22 on which an original24 to be copied is mounted. The reciprocating carrier 18 is adapted tomove the original back and forth past the light 26 (also identified asLl) which illuminates the copy. The movement of the carriage 18 issynchronized with the rotation of the drum 14 such that the peripheralspeed of the drum and the linear motion of the carriage 18 areidentical. As copy passes by the lens 28 the image is focused upon thesurface of the photoconductive layer 16. A mirror 30 which may be aprism if desired directs the image at right angles to the surface of thephotoconductive layer 16. The limits of the path of travel of thecarriage are determined by limit switch LS1 in the direction to theright as viewed in FIG. 1 and limit switch LS2 as viewed to the left inFIG. 1. It is understood, of course, that switch LS2 is positioned muchfurther to the left, a part of the support being shown broken awaybecause of space limitations on the drawing. Drum 14 is mounted on theshaft 32 and its surface is in contact with rollers 33, 34, and 35,which are positioned in a tank 36 containing the developer liquid 38 ofour invention.

A motor M2 is adapted to drive an agitator 40 to keep the developerliquid agitated so that the insoluble components of the developer willremain dispersed throughout the developer liquid. A shaft 42 carriesroll of paper 44 or other flexible sheet material to which the copy isto be transferred. A motor M3 drives a centrifugal fan 46 to furnish airto an elongated nozzle 48 adja cent the periphery of the drum 14 toremove excess developer liquid from the surface 16 of the drum. Aplurality of hot air manifolds 50, 52, 54 and 56 are controlled byrespective valves connected to a supply of hot air (not shown). Hot airfrom manifold 50 is directed against the surface 16 of the peripherydrum l4. Manifold 52 directs hot air to the side of the paper which isto receive the transfer from the drum. Manifold 54 directs hot air onthe opposite side of the paper. Manifold 56 directs hot air to thefinished transfer after it has been severed from the roll by knife 60operated by; solenoid S2. Paper is drawn from the roll 44 by takeoffroller 62 and the cut sheet is fien moved by delivery roll 64. As willbe pointed out hereinafter the positions of the respective valvescontrolling the hot air may be varied depending upon the particularcomposition of the developing liquid being used. The use of hot airmanifolds are beneficial but not absolutely essential for the practicingof our method. They are particularly useful where high-speed operationand a rapid reproduction rate is desired. A corona discharge device 66(K) is positioned adjacent the photoconductor surface of the drum tocharge its surface in the dark. A cleaning roller 68, which may be wetif desired, removes any residual toner which may be inadvertently lefton the surface of the drum.

Shielded light 70 (L2) insures that a residual electrostatic charge isconducted to ground before the surface of the drum is recharged.

Referring now to FIG. 2 the moving parts of our photocopier are drivenfrom a prime mover to be indicated by the reference numeral and a motorM1. The motor 100 drives a shaft 32 which carries for rotationtherewith, a first-gear wheel 102, a second-gear wheel 104 and a pinion106. A shaft 31 carries a pinion 108 for rotation therewith. A pinion110 which is loosely mounted'on shaft 31 engages a rack 112 which iscarried by and secured to the carriage 18. A clutch C1 is secured toshaft 31 for rotation therewith. A pinion 114 is mounted on a side shaft39 for rotation therewith. Pinion 107 is driven by shaft 31 and drivespinion 109 which drives pinion 111 to drive shaft 39. Pinion 114 is inengagement with the pinion 116 which is mounted for rotation with shaft29 which shaft carries a clutch C2. it will be seen clutch C1 rotates inone direction and clutch C2 rotates in the opposite direction. Whenclutch C1 is energized it will engage the loosely mounted pinion 110 anddrive the rack 112 in one direction. When clutch C2 is energized it willengage the pinion 110 and drive the rack 112 in the opposite direction.The pinion 108 is driven from the gear 102 by gear chain 120. The pinion106 drives the pinion 122 through a gear chain 124. This drives theroller 34. Rol lers 33 and 35 are driven through intermediate gears 123,124, 125, 126 and 127. The developer applying rollers 33, 34 and 35rotate in the same direction. The ratio of the gear chain and pinions issuch that peripheral speed of the rollers 33, 34 and 35 is the same asthe peripheral speed of the drum 16. A takeoff roller 62 is mounted on ashaft 61 for rotation therewith. A clutch C3 is mounted on the shaft 61for rotation therewith. The shaft 61 carries a pinion 128 loosely sothat the pinion may rotate freely. The pinion 128 is driven by gearchain 130 from the gear wheel 104. When the clutch C3 is energized thetakeoff roller will rotate. A pinion 132 is driven from the pinion 128by a gear chain 134. It rotates continuously and is mounted on the shaft63 which carries the delivery roller 64.

Referring again to FIG. 1 the paper on which copy is to be made passesfrom the roll 44 over printing roller 43 mounted on a shaft 41. Theshaft is carried by a pair of links 45 pivotally mounted on a shaft 47.When the arcuate solenoid S1 is energized the links move downwardly tobring the paper into contact with the rotary drum to effect the transferof the developed image to the paper.

Referring now to FIG. 3, which shows the control circuit for our copier,at the start of an operation limit switches LS1 and LS2 are in thepositions shown in the drawing. The carriage 18 is to the right asviewed in FIG. 1. An original sheet to be copied is placed upon thetransparent plate 22. The machine is energized by closing switch TS. Themain lines 200 and 202 are connected across an appropriate source ofpotential. The closing of the switch TS energizes the main motor [V1 1,the blower motor M3 and the agitator motor M2. it also energizes theerasing light L2. To start the operation of the copier, push button PBis pressed just momentarily. This completes a circuit through the relaywinding 1R and closes normally open relay contacts 1R1, 1R2 and 1R3. Thecontact 1R1 completes a holding circuit through LS2 and maintains therelay winding 1R in energized condition. The circuit through contacts1R2 energizes clutch C1 and drives the carriage to the left as viewed inFlG. 1. The circuit through contacts 1R3 energizes the light L1 and thecorone discharge device K. The original passes by the light and an imageof it is focused upon the moving drum by the lens 28 and the mirror orprism 30. A latent electron image is impressed upon the photoconductorsurface 16 as is known in the art. This latent image is later developedby the developing liquid owing to the movement of adhesive tonerparticles suspended in the developing liquid to the charged portions ofthe drum. The air knife blows excess developing liquid from the drum. Asthe carriage 18 moves to the left it'strikes limit switch LS2. Thisswitch now moves downwardly from the position shown in FIG. 3 to breakthe holding circuit through 1R1 and thus opens the circuits through 1R2and 1R3. The opening of the circuit through 1R2 de-energizes clutch C1.The opening of the circuit through 1R3 deenergizes the corona chargingcircuit K and deenergizes the illuminating lamp Lll. A circuit is nowmade through winding 2R. The energization for winding 2R closes circuitthrough 2R1, 2R2, 2R3 and 2R4. The closing of the circuit through 2R1completes a holding circuit and maintains the winding 2R energized, thecircuit now being completed from main 200 through winding 2R throughcontacts 2R1 through normally closed contacts 3R1 to the other side ofthe line 202. The closing of contacts 2R2 energizes clutch C2 throughnormally closed (in the position shown) limit switch LS1 and drives thecarriage 18 in the reverse direction. The closing of contacts 2R3energizes solenoid S1 to draw the printing roller 43 downwardly againstthe action of the spring 49. The tacky toned image is then transferredto the paper. The clutch C3 is also energized so the take-off roller 62will rotate to draw the paper from the roll and pass it to the rightthrough the delivery rollers 64. As can be seen by reference to FlG. 1both the rollers 62 and 64 have backup rollers against which they bear.The closing of contacts 2R4 partially completes a circuit throughwinding 3R. When the carriage on its return to the right strikes limitswitch LS1 it moves it from its normal position shown in FIG. 3upwardly. This completes a circuit through winding 3R. Energization ofwinding 3R closes the contacts through 3R2 and energizes solenoid S2which operates the cutting knife 60. it also breaks the holding circuitthrough winding 2R. This permits contacts 2R1, 2R2, 2R3 and 2R4 toreassume their open positions. When contacts 2R4 are broken the relaywinding 3R is de-energized and contacts 3R2 are opened to de-energizewinding of solenoid 52. It will be understood, that while we havedescribed the cycle for a single operation, successive cycles to anydesired number may be initiated by a sequencing means known to the art,whereby the cycle will be repeated as desired to make multiple copiesautomatically. This can be easily accomplished by having a sequencingswitch act to close the circuit through PB completed by a synchronousbrush instead of by a push button. It is to be understood, of course,that the limit switches are biased by the appropriate means such assprings to assume the positions shown in FIG. 3 at the end of a cycle ofoperations.

Referring now to FIG. 4, we have shown a modified fonn of the machineshown in HO. 1. lnstead of a drum carrying a photoconductive layer weprovide a belt 300 having a photoconductive layer 16. The belt is passedaround a pair of conductive drums 302 and 304. The sheet material towhich the image is to be transferred passes from roll 44 over guide roll306 under guide roll 308 around the belt 300 carrying thephotoconductive layer 16 and then over guide roll 310 to takeoff roller62.

In the form of the invention shown in FIG. 4 an elongated manifold 33heats the rear side of the copy paper by hot air delivered to themanifold and controlled by a valve. The cleaning roll in the form of theinvention shown in'FlG. 4 is disposed in a tank 69 containing cleaningfluid 71 so that the cleaning roll 68 may remove residual toner whichmay inadvertently or accidentally adhere to the photoconductor surfaceof the belt.

The belt may be made of any appropriate material which is flexible andconductive such as wire mesh, fibers of synthetic resin impregnated withconductive material and woven into a belt, or flexible metallic screen,or the like. The photoconductive layer will be described more fullyhereinafter. It will be recognized that the arrangement shown in FIG. 4is essentially the same as that shown in FIG. 1, except that a belt isused instead of a drum. Since the imaging station is removed from thetransfer station, it is not necessary to use a solenoid S1 to bring thecopy paper into contact with the drum.

Referring now to FIG. 5, the arrangement is quite similar to that shownin FIG. 1, except that instead of transferring a toned image from thephotoconductive layer 16 to sheet material, the transfer is made onto aconductive drum 400 mounted on a shaft 402. The transferred imageindicated at 403 is fixed by a radiant heater 404.

Referring now to FIG. 6, the drum 400 having the image 403 thereon ismounted on a shaft 406. The toner-formed image 403 is non-conductive sothat when it is charged by the corona discharge from corona dischargedevice 60 only the image will retain the charge. The charge elsewhere ondrum 400 will be conducted to ground since it is conductive.Accordingly, when the charged image is subjected to the developersolution as fed by the rollers 33, 34 and 35 from the toner liquid inthe tank 36, the drum will act as a printing drum and transfer thefreshly toned portion of the image 403 on the paper drawn from the roll44. It will be observed that this operation may take place inbroaddaylight since no photoconductive phenomenon is involved. The charge isretained on the non-conductive image formed by the toner particles andthe charge upon the image will pick up toner and transfer the tonerimage to a portion of the roll of paper or other sheet materials. It isto be understood, of course, that the printing drum 400 may be providedwith a cleaning roller 68.

The developer according to the present invention is so arranged that itis more adhesive in respect of the surface-to which it is to betransferred than it is to the surface on which the latent image isproduced. Accordingly, when the latent image is developed it can readilybe transferred to the copy sheet because of its greater affinity for it.

In its simplest aspect we may give the photoconductive surface lowadhesion by treating the same to provide a silicone or a urethane film.Similarly it is feasible to treat paper with a medium which will givethe paper a physical affinity for the toner, that is, the developedtoner image. In a similar manner it is possible to cool thephotoconductive surface and heat the copy paper. This temperaturedifferential will have the effect of enhancing the affinity of thedeveloped image with a copy paper.

To make a photoconductive surface for the drum 14 or the conductive belt300 which will have a low affinity for the developed image we proceed ina number of different ways to accomplish this result.

EXAMPLE 1 Prepare a mixture as follows:

1.000 gms. of Zinc Oxide gms. of short oil (safflower) oxidizing alkydresin.

210 gms. of unmodified melamine formaldehyde resin solution in butanolhaving a solids content of about 58% and a specific gravity of about[.02.

mls. of Butanol 480 mls. of Toluol 300 mls. of Chlorothene Dyes may beadded to the above mixture, as is well known in the art, to obtain therequired photosensi- -tivity. This mixture is then ballmilled for 12hours. It is then diluted with the following solution:

300 mls. of Chlorothene 300 mls. of Toluene 300 mls. of Butanol 1.2 gms.of Cobalt Naphthenate (as a dryer).

2.4 gms. of Lead Naphthenate (as a dryer).

This mixture is then applied to the drum or the belt and cured. Aftercuring, a thin film of an emulsion of a silicone resin together with anappropriate catalyst such as lead monoxide, benzoyl peroxide or thelike, is mixed in a light hydrocarbon (boiling range 60 C C) and isapplied over the photoconductive surface. The catalyst is used to theextent of IO percent of the resin and the film concentration is coatedat 8 percent. The film is then cured from 4 to 6 hours at C or 16 to 32hours at 71 C. Tests made on a photoconductive surface as described inthis example enabled a total of 800 images to be developed on 6 feet ofbelt and transferred to copy paper at the rate of 42 feet per minute.

EXAMPLE 2 gms. of gms. of

19 gms. of

8 gms. of

40 mls. of

of of mls. mls.

The above mixture is then ballmilled with dyes to obtain the requiredphotosensitivity as is known in the art and diluted with:

40 mls. of hydrocarbon solvent having a boiling range between l00 C and120 C. 70 mls. of Toluol 0.2 gms. of Cobalt Naphthenate used 0.8 gms. ofLead Naphthenate as 1.6 gms. of Zirconium Octoatc dryers It will beobserved that the silicone resin is now combined with thephotoconductive zinc oxide and a binder EXAMPLE 3 Zinc Oxide short oil(safflower) oxidizing alkyd resin.

an emulsion of silicone resin ballmilled with an appropriate catalystsuch as lead monoxide, benzoyl peroxide, or the like. hydrocarbonsolvent having a boiling range between 100 C and 120 C. Terpineol 100gms. of 27 gms. of

20 gms. of

10 mls. of

10 mls. of

The above mixture is then ballmilled with dyes to obtain the requiredphotosensitivity as is known in the art and diluted with:

40 mls. of hydrocarbon solvent having a boiling range between 100 C and120 C.

10 mls. of Toluol l mls. of Terpineol 0.2 grns. of Cobalt Napthenateused 0.8 gms. of Lead Naphthenate E as 1.6 grns. of Zirconium Octoatcdryers This mixture is then applied to a substrate and cured.

EXAMPLE 4 1,000 gms. of Zinc Oxide 415 gms. of Polyurethane Alkyd Resin400 mls. of Toluol 400 mls. of hydrocarbon solvent having a boilingrange between 100 C and 120 C.

Dyes are added to obtain the required photosensitivity and the mixtureis then ballmilled as in EXAM- PLE 1. It is then diluted with:

300 mls. of Toluene 300 mls. of hydrocarbon solventhaving a boilingrange between 100 C and 120 C. 300 mls. of Chlorothene 3 gms. ofsuitable dryers such as Cobalt Naphthenate, Lead Naphthenate andZirconium Octoate.

The mixture is then coated on the substrate and cured as before.

It will be observed that in the above examples the photoconductivematerial which is coated on the drum or the belt substrate is compoundedso that the photoconductive layer will have a reduced adhesion for thetacky toner.

Ordinarily, it is more desirable to be able to employ untreated paper asthe copy sheet to which the tacky tonered image is to be transferred.However, it is also contemplated by our invention that a paper treatedto ve ses aifia ty for t e a yto r ear hs aployed. For example, we havetreated the paper with a solution of an maleic acid-modified vinylchloride and vinyl acetate copolymer. The solvent is evaporated and itwill be found that the paper thus treated has a special affinity for thetacky tonered image.

Another example of a coating for paper is a solution of a vinyltoluene-butadiene copolymer resin. These resins are available from theGoodyear Tire and Rubber Company and sold under the trademark PLIO-LITE. They are soluble in aliphatic solvents and films are formed bysimple evaporation of the solvents. A paper coated with PLlOLITE resinexhibits affinity for the tacky tonered image. Another example of acoated paper is one coated with a solution of polyvinyl butyral. Thissynthetic resin is dissolved in alcohol to form a 4 percent solution. Itis then applied to the paper to form a thin continuous film. Theaffinity for the toner in each case of the paper coated with theexamples given above was such that transfer took place from thephotoconductive layer to the paper. It is of interest to note that thepressure to effect the transfer is very slight. As a matter of fact iftoo much pressure is used it was found that the transfer of the toneredimage from the photoconductor to the paper was less effective.

It it not necessary that the developer deposit a toner in a tacky orsticky condition. The developer may be such that the tonered image isnon-tacky at first then becomes tacky or adhesive so it can betransferred in atacky state and then as the solvent evaporates, dries orcures and loses its stickiness and remains firmly bonded to the surfaceto which it was transferred.

According to our invention the adhesive toner comprises a relativelylarge amount of a high molecular weight polymer adapted to form acontinuous pigmented polymer matrix exhibiting high cohesion andtackiness. In general, high molecular weight polymers are dissolved in asuitable solvent. The solution of the high molecular weight polymer ispigmented with a suitable pigment such as microlith black and thesolution suspended in a low-power solvent or diluent with the aid of adispersing agent. The high molecular weight polymer may be one which hasa low adhesion for the image forming surface and a high affinity for thecopy surface. Alternatively the high molecular weight polymer may havelow adhesion for both surfaces and a tackifier is combined with thepolymer to create the high adhesion for the copy paper. The maincharacteristic of the high molecular weight polymer, however, is that itis generally insoluble in the diluent which we employ in making ourdeveloper fluid. The diluent which we prefer is that manufactured by theStandard Oil Company of New Jersey and sold under the trademark lSOPARG." This is an isomerized paraffinic hydrocarbon having a specificgravity of 0.75 at F. This product is substantially percent pureisoparafiin. it has a boiling range from 157 C to 177 C. ISOPAR H is asimilar product and has a boiling range from 177 C to 188 C. This isdisadvantageous in that it takes a longer period of time for the copiesto dry. The feature which characterizes the diluent is that it has lowsolubility for the solution of the high molecular weight polymer whichis suspended throughout the diluent by a suitable dispersing agent.lSOPAR G has a kauributanol number of 27. This is true of lSOPAR E"which has an initial boiling point of 1 16 C and a final boiling pointof 143 C. lSOPAR E, however, is dangerous to use since it has a flashpoint of 50 F. The flash point of lSOPAR G is F, and it is therefore asafer diluent. Because the tacky toner particles must migrate throughthe diluent under the influence of an High Molecular Weight ResinsManufacturer Trademark Vinyl-toluene/acrylate Goodyear Tire PLIOLITEVTAC" copolymer* & Rubber Co.,

Akron, Ohio Styrene/acrylate Goodyear Tire PLlOLlTE AC" copolymer &Rubber Co. Styrene copolymer Goodyear Tire PLlOLlTE S-SA"Butadiene-styrene Phillips SOLPRENE" copolymer" Petroleum Co.

Solutions of this resin in solvents having Kauri-butanol values of 36and higher dry rapidly to form tough. hard film with good adhesion.Furthermore. a solution of this resin will not dissolve in ISOPAR G"(which is one of our diluents) which has a kauri-butanol number of 27.

" "SOLPRENE 303" is a solution-polymerized copolymer in the ratio of52/48 with partial block distribution of the styrene along the molecularchain. SOLPRENE 1205" is a copolymer of butadicne and styrene in theratio of 75/25 manufactured by the solution polymerization process.

These resins are readily soluble in hydrocarbon solvents having highkauri-butanol numbers of 50 or more. An appropriate solvent is thehydrocarbon solvent manufactured by Standard Oil Company of New Jerseyand sold under the trademark SOLVESSO 100. It has an initial boilingpoint of 159 C and a final boiling point or end point of 182 C. Itconsists largely of aromatic hydrocarbons and has a kauri-butanol numberof 91. it is to be understood that any appropriate solvent may beemployed. However, since some of the solvent for the resin will bepresent in the developer solution, its end point should be low.

As is pointed out above, ISOPAR G has an end point of 177 C. SOLVESSO100 has an end point of 182 C. SOLVESSO 150 could be used, if desired,but it has an end point of 212 C. The particular solvent is not criticalas long as it is a solvent for the high molecular weight resin and canbe evaporated at convenient temperatures from the final developersolution.

While the high molecular weight resins we employ exhibit tackiness upondrying, that is, when they are al- Tackifier Resins ManufacturerTrademark Polymcrized alpha Pennsylvania PICCOLYTE pinene IndustrialALPHA Chemical Corp. Polymerized beta Pennsylvania "PICCOLYTE pineneindustrial BETA" LCQE UE EQ Tackifier Resins Manufacturer TrademarkChemical Corp Polymerized mixed Reichhold STA-TAG" olefins* Chemicals.

Inc. Heat-reactive synthetic Reichhold BETAPRENE BC hydrocarbon polymersChemicals.

Inc. Pentaerythritol ester Hercules lnc. PENTALYN H" ofhydrogenatedrosin These provide performance qualities comparable to those achievedby pure terpene resins.

" These polymers have iodine numbers of about 130. but the double bondsare structurally protected and not easily crosslinked or oxidized. Theybehave much like terpene resins and provide good wetting properties andadhesion to a wide variety of surfaces.

The high molecular weight resins may be plasticized to render them tackyby modifying agents. These are:

Plasticizers for High Molecular Weight Resins Manufacturer TrademarkDibutyl phthalate Celanese Corp.

of America Dioctyl phthalate Celanese Corp.

of America Dimethyl phthalate Diethyl phthalate Di-isobutyl phthalateDi-iso-octyl phthalate Chlorinated polyphenyl Monsanto Chemical CompanyUnion Carbide Plastics Co.

AROCLOR I254 Tricresyl phosphate Some of the high molecular weightresins, such as PLIOLITE VTAC," do not possess sufficient tackiness toeffect complete transfer. We have seen that a tackifier resin may beadded compatible with the high molecular weight resin to give theorganosol the desired tackiness. This tackiness can be achieved byadding plasticizers to the high molecular weight resin. Theseplasticizers have the property of imparting tackiness to the highmolecular weight resin so that less or no tackifier resin may beemployed.

In carrying out our invention, we first manufacture the organosol bydissolving a high molecular weight resin or a mixture of high molecularweight resins in an appropriate solvent.

EXAMPLE A The following formulation is prepared:

37.5 gms. PLIOLITE VTAC 40.0 gms. SOLPRENE 1205" 100.0 grns. SOLVESSO Aswe have pointed out above, SOLVESSO 100 is an ideal solvent. Any otherappropriate solvent such as terpineol can be employed. The aboveformulation is emulsified in a high-speed emulsifying mill, togetherwith l 100 mls. of a diluent such as ISOPAR G. A quantity of thisorganosol is further diluted with ISOPAR G to any desired extent to forma suspension. This suspension produces a tacky resin deposit on anegative polarity electrostatic surface charge.

The toner component is formulated to be compatible with the resinorganosol, since it must be physically attached to the resin developeraggregates or co-deposit resins used were PLIOLlTE VTAC and SOLPRENE1205. The pigment may be of any desired nature as, for

example, carbon black, having a particle size on the average of 25millimicrons. Any desired pigment may be used as, for example, reflexblue pigment with the carbon black. The pigment is advantageously coatedwith a modifying resin or a drying oil. A toner matching the organosolof this Example A is as follows:

100.0 gms. microlith black 12.5 gms. reflex blue 25.0 gms. PLIOLITE VTAC25.0 gms. SOLPRENE 1205 Sufficient toluol was added to the above mixtureto achieve the correct milling viscosity for milling in a triple-rollmill. After milling, the mixture was diluted with 600 mls. of ISOPAR G.This toner is effective for negatively charged electrophotographicimages.

The resin organosol and the toner component are mixed in a high-speedemulsifying mill and" the constitu'- ents milled together. The resinsolution repared as described above was diluted with 1100, ls. of ISOPARG and milled for one minute. Then 120 mls. of the toner component wereadded and the mixture milled for three additional minutes. Thisconcentrated adhesive toner was further diluted in a ratio of 50 mls. oftoner to 200 mls. of ISOPAR G to produce a developer liquid. Adhesive ortacky toner in this developer liquid is readily deposited on a negativepolarity surface charge. It will be understood that there isnothingcritical in the method of mixing the components; The tonercomponents may first be added to the mill with 1100 mls. of ISOPAR G andthen followed by mixing with the resin solution. Alternatively, theresin and the toner may be combined and then added to the mill with thediluent.

This adhesive toner developing liquid produced good image transferbetween an organic photoconductor and an uncoated paper such as VelvetBook Opaque. It also produced good transfer between a zinc oxide-resinphotoconductor and a Velvet Book Opaque paper. A low density image wasobserved on the zinc oxide photoconductor after transfer. Thephotoconductive surface was a commercial zinc oxide photoconductorandnot one of our special non-adhesive formulations as described above.

We then formulated another organosol component as follows: 7

EXAMPLE B 37.5 gms. PLlOLlTE VTAC 20.0 gms. BETAPRENE BC 100 which is'atackitier resin 100.0 gms. SOLVESSO 100 The addition of the tackifier tothe resin component and its incorporation into the developing fluid inthe manner identical to that described above produced a developing fluidin which the image transfer from the organic photoconductor to theVelvet Book paper was less complete. On the other hand, when this tonerwas used with art paper, the transfer was more complete. it is to beunderstood, of course, that the photoconductors tested were not of thetype of our invention having a low adhesion. When these toners weretested with photoconductors of our invention, the transfer of our tackytoner from the photoconductive surface to the paper wassubstantiallycomplete.

The amount of toner component combined with the organosol componentchanges the adhesive properties. With 120 mls. of toner component,optimum adhesive transfer properties were achieved. The toner componentin the amount of 60 mls. produced a deposit of low optical density andthere was greater sedimentation of the toner concentrate. A tonercomponent of 240 mls.

' produced an optically dense deposit. The cohesion and adhesion werelowered with a resultant loss of transfer properties.

EXAMPLE C An organosol was formed as follows:

37.5 gms. SOLPRENE 303 20.0 gms. PICCOLYTE ALPHA 10.0 gms. Polystyrene(melting point C; approximate molecular weight 400) 100.0 gms. SOLVESSOThis resin mixture is milled in a high-speed emulsifying mill togetherwith 1100 mls. of a diluent such as ISO- PAR G. This forms the resinsolution or organosol.

The toner component matching the Example C organosol was made asfollows:

75 gms. SOLPRENE 1205 Tiara a cga'a'a triple r oll inill ahd sufticienttol uol was added to dissolve the mix and produce good millingviscosity. The mix was then diluted with 1200 mls. of ISOPAR G in ahigh-speed emulsifying mill. The resin mix was added to 1 100 mls. ofISOPAR G in a high-speed emulsifying mill, to which was then added mls.of the toner componentType C. This produced a developing liquid of ourinvention which exhibited low adhesion for both the organic and zincoxide photoconductors and high adhesion for bond paper, Velvet Bookpaper, and art paper.

It will be observed that in each case the toner component is compatiblewith the organosol, so that the high molecular weight polymer nucleatesor attaches to the toner component. In order to achieve this, thepigment must be wetted with a material which allows compatibility withthe high molecular weight polymer. After the toner component is milled,it is tested for its electrophoretic properties. The tests varieddepending on the type of pigment employed. Some tests showed that tonercomponents deposit both on negatively and positively chargedelectrostatic surfaces. A toner compo- An example of this follows:

EXAMPLE D An organosol was confected as before from the following:

37.5 gms. PLIOLITE VTAC 20.0 gms. BETAPRENE BC-IOO 100.0 gms. SOLVESSO100 The matching toner component was made as follows:

50 gms. carbon black (particle size 25 millimicrons) mls. of ISOPAR G ina high-speed emulsifying mill and milled for three minutes.

The resultant adhesive toner concentrate was diluted in the ratio of 50mls. concentrate to 200 mls. of ISO- PAR G to produce an adhesivedeveloping liquid. This adhesive developing liquid produced a deposit onnegatively charged zinc oxide photoconductor which was then transferredcompletely to uncoated bond paper. This formulation is characterized bya high-yield elec trophoretic deposition on a negative polarity chargedsurface. The pigment to resin ratio of this tone is approximately 1:6.

It will be seen that a high molecular weight polymer may form a solutionwhich may be then suspended in a diluent having low solvent power.PLlOLlTE VTAC acting by itself exhibits good adhesion to most surfaces.We can modify the adhesive properties by using other high molecularweight polymers which in themselves have a lower adhesion for mostsurfaces. Adhesion can be increased by addingtackifier resins whichimpart additional adhesion to high molecular weight polymers.Plasticizers may be added to modify the adhesive properties, if such bedesired. 1

The pigment component acts to reduce sedimentation of the tonerconcentrate. Our tacky toners generally comprise relatively largeaggregates 'andconsecopy paper. The resins and plasticizers which arechosen must be insoluble in the diluent which suspends the organosol andthe toner formulation.

transfer method of a developed electrostatically formed image utilizesthe tackiness of the toner and does not depend on an electrostaticfield. We have provided a method of contact transfer of a liquid tonerdeveloped electrostatic image from a photoconductive surface to a copysheet while maintaining the conductive surface in a clean condition. Wehave provided a liquid developer which has greater affinity for the copypaper than the photoconductive surface on which the image was formed. Wehave provided a photoconductive surface which has less affinity for thedeveloped electrostatic image than for the paper to which it is to betransferred. We have provided a novel developing liquid carrying insuspension a toner which is nonsticky when first deposited, whichbecomessticky or tacky after deposit, so that it can be transferred in itstacky condition, and which then loses its tackiness so that it remainsfirmly bonded to the surface to which it is transferred. We haveprovided a novel apparatus for .carrying out our novel method. We haveprovided a novel sheet material having a special affinity for a tackytoner developed image.

It will be understood that certain features and subcombinations areofutility and may be employed withquently suffer greater sedimentationthan liquid toners of the prior art. This, however, does not presentpractical problems as long as the sediment is flocculent, since suchflocculent sediment is easily redispersedby mechanical agitation. It isfor this reason that we have out reference to other features andsubcombinations. This is contemplated by and is within the scope of ourclaims. It is further obvious that various changes may be made indetails within the scope of our claims with out departing from thespirit of our invention. It is, therefore, to be understood that ourinvention is not to be limited to the specific details shown anddescribed.

' Having thus described our invention, what we .claim is:

l. A method of electrophotography including the steps of charging aphotoconductive surface, exposing the photoconductive surface to producea latent electrostatic image, subjecting the image to a developingliquid having a tacky toner organosol suspended therein to form avisible transferable tacky image on said surface, and then contactingthe tacky image while in a sticky state with sheet material to transferthe image substantially completely from the photoconductive surface tothe sheet material by the adhesiveness of the developed image.

2. A method as in claim 1 including the step of heating the sheetmaterial before thecontacting step.

3. A method as in claim 1 including the step of heating the visibletacky image prior to the contacting step.

4. A method as in claim 1 including the steps of heating the tacky imageprior to the contacting step and heating the sheet material prior to thecontacting step.

5. A method a in claim 1 including the step of decreasing the affinityofthe photoconductive surface for the tacky image. a

6. A method as in claim 1 including the step of increasing the affinityof the photoconductive surface for creasing the affinity of the sheetmaterial for the tacky the tacky toner and increasing the affinity ofthe sheet image. material for the tacky image.

7. A method as in claim 1 including the steps of de-

1. A METHOD OF ELECTROPHOTOGRAPHY INCLUDING THE STEPS OF CHARGING APHOTOCONDUCTIVE SURFACE, ECPOSING THE PHOTOCONDUCTIVE SURFACE TO PRODUCEA LATENT ELECTROSTATIC IMAGE, SUBJECTING THE IMAGE TO A DEVELOPINGLIQUID HAVING A TACKY TONER ORGANOSOL SUSPENDED THEREIN TO FORM AVISIBLE TRANSFERABLE TACKY IMAGE ON SAID SURFACE, AND THEN CONTACTINGTHE TACKY IMAGE WHILE IN A STICKY STATE WITH SHEET MATERIAL TO TRANSFERTHE IMAGE SUBSTANTIALLY COMPLETELY FROM THE PHOTOCNDUCTIVE SURFACE TOTHE SHEET MATERIAL BY THE ADHESIVENESS OF THE DEVELOPED IMAGE.
 2. Amethod as in claim 1 including the step of heating the sheet materialbefore the contacting step.
 3. A method as in claim 1 including the stepof heating the visible tacky image prior to the contacting step.
 4. Amethod as in claim 1 including the steps of heating the tacky imageprior to the contacting step and heating the sheet material prior to thecontacting step.
 5. A method as in claim 1 including the step ofdecreasing the affinity of the photoconductive surface for the tackyimage.
 6. A method as in claim 1 including the step of increasing theaffinity of the sheet material for the tacky image.
 7. A method as inclaim 1 including the steps of decreasing the affinity of thephotoconductive surface for the tacky toner and increasing the affinityof the sheet material for the tacky image.